>> This is not true. First of all, there are more than two species of
megapodes
>> (22 according to the latest monograph).
>
>Yes, but only a fraction of these are hole-nesters--I think this is the
>term I should have used rather than "fossorial". I realize the birds you
>listed are fossorial but they all (don't they?) manipulate the nest during
>incubation.
I'm not sure what you mean by "manipulate the nest". Of the 22 megapodes, all
bury their eggs, either in mounds which they construct or burrows; in the
latter case the eggs are heated either by geothermal or by solar radiation.
There are seven species of megapodes known or suspected to use burrows. In
three of these, the Maleo Macrocephalon maleo, the Moluccan Megapode Eulipoa
wallacei, and the Polynesian Megapode Megapodius pritchardii,
burrow-nesting is
the only known type.
In the monograph on the family by Jones, Dekker and Roselaar (The Megapodes:
Oxford UP 1995) the authors compare them to other underground-nesters, noting
that some birds like the Egyptian Plover will bury their eggs to prevent
overheating or water loss. They note that crocodilians are the only reptiles
to construct incubation mounds, but that they "do not appear to manipulate
their mounds like megapodes, so the prevention of overheating may be
limited to
the careful selection of the site". I recommend this book for many details on
the physiological and other adaptations of megapodes to underground incubation
(there is also a chapter on the evolution of the megapode incubation system,
which the authors agree is secondarily derived from normal bird patterns.
>In fact megapodes are unique in that they don't do _anything_ for
>hatchlings. Post-hatchling care is, I believe, a uniting trait of all
>other birds. And Coombs (in _Modern analogs for dinosaur nesting and
>parental behavior_) argues that such hatchling independence and the long
>incubation and predator-friendly vegetation mounds "necessitates nearly
>total freedom from egg predation."
I should note that most places where megapode nests are found are
comparatively
predator-free; in Australia, introduced foxes take a heavy toll on eggs and
young, and some have speculated that megapode distribution generally is
restricted by the presence of predators. So the megapode system does not
appear to confer much of an advantage vis-a-vis nest predation compared to
that
of other birds.
--
Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2 mailto:ornstn@inforamp.net